Sinuous wire element as extended surface on undulated heat exchanger plate wall



March 2, 1954 s HOLM ET AL 2,670,936

SINUOUS WIRE ELEMENT AS EXTENDED SURFACE 0N UNDULATED HEAT EXCHANGER PLATE WALL Original Filed June 5, 1947 'gases'a-n'd constituted-'by'parts of specially formed -be"undesira'bly--large.

Patented Mar. 2, 1954 sinuous wins-ELEMENTssffiiiiehblm suarncaonrnunummn HEAT x- CHANGER PLATE WALL ' assignorsto The' Air New-York; NJY.

lreheater 'Gorporation,

"ioiisiiiai "tributaries" June .3; .1947, saiaf so.

' 7523008,:hQW Patent No". 2,595,457, 'datedMay this application October 2e, 19s1;=seris1-No. -252,6 2

- e oaims (01. ear -25s) I Thisinvention relates particularly te -improvements in extended surface for h'eat exchange apparatus in the form of pin-like fins projecting from plate suriaces intothe path of the heating wireeleme'nts attached to the; plates. A' 'heat exchanger'capable of transferring large j quantities' cfheat between a gas and air or the 1 like, asin a gasturbine plant; becomesa rather *bulky pieceof equipment if designed" as a shell and tube-typeheat exchanger. Apllatetype exchanger might occupy less space but even a whenprovided with conventional finned 1 surfacesof types heretofore employed it would still To attain areau compact heat "exchanger design it- 'is 'desirable to haveheat absorbing surfacein=contact-with*each fluid of at least '100-sq. ft. per cubicfoot of 'volurneloyutilifing extended-surface. The present invention conforming plates have thicknesses of around a quarter-to one half the iin diameter.

:Amgbiecfi i sie tiqe is re -Wide an improved form of pin-iiri extended surface for use in a heat exchanger.

Other objects and advantages of the invention will become apparent upon consideration of the following detailed description of illustrative embodiments of the invention when read in conjunction with the accompanying drawings in which:

Figures 1 and 4 are fragmentary perspective views of a small part of a plate type heat exchanger illustrating extended surface made up of specially formed wire elements each attached to the heat exchange surfaces at a multiplicity of points and in good heat conducting relationship therewith.

Figures 2 and 5 are partial plan views and Figures 3 and 6 are fragmentary sectional views corresponding to Figs. 1 and 4 respectively.

Referring now to the drawings, the heat exchanger consists of a series of metallic plates 26, 2|, spaced to form gas and air passages 22 and 23 disposed in alternating arrangement. As customary in plate type heat exchangers the sides of the gas and air passages are suitably closed; as by providing fillers or joining the edge portions of 'adja-cent" plates in: alternation along their side and endedges; In accordance with'the present inventiongthereare located in 5 th'ega-s passages'fi and secured to thega's'side -ofthe plates 20, 2|, a plurality'of' heat exchange elements designated as a whole by the numeral 49. Each element 49 consists-of a continuous length of *sinusoidally bent wire 'havinga plumaIity-of'zig-Zag' bends or loops or roughly U- shape and formed into a coil The' 'fin elements to be described all consist essentially of wires with zi'g zags or bends'therein and as illustrated in-Figures 1 and 4;: consist f of wires 'whichh'ave'been formed so thatthe su'ccessive'loop or bend is disposed parallerwith --loops contiguous thereto; "The 'stretchers' or yokes "-46; 4?" that connect thelegs 48 at the top and bottom of'the loops are 'in"contact with" and "bonded to the'*p1ates*20,'=2l' respectively; that constitute oppositewalls' of a gas "passage.

In' "the construction illustrated afurther ini'crease the 'amciint of heat exchange surface is P attained first by corrugating "the wall plates 20,

" 2i which obviously increases their area and "secondly, by fastening the wire element's 49fin the "bases of f'the grooves 42; of the corrugated plates so that a closer spacing of elements may be'pi-ovidedi Since t'hfolm shown utilizes plates'w'ith corrugations of the'same'radius-as'the wire which -is' brazed ors'e'amweldedthereto it thereforeizdoes not necessarily require aisfiattened out' portion on the wire because a sufficient area of contact is obtained between the surface of the wire and the groove'of like radius in the plate.

In Figures 1 to 3 the plates 20, 21 are undulated have the axes of their undulations disposed oppositely or crossing to increase the turbulence 3 along their surfaces so as to break up the boundary layer or film. The successive yokes 46, 4'! of each wire element 49 are located at approximately 90 with respect to each other so that they may be brazed or welded in the valleys of 45 the undulations in the plates forming opposite walls of the passage in which they are located.

In Figures 4 to 6 the angles between the yokes are greater so that for counterflow of the two fluids the angles (about 30) of the yokes with 0 respect to the direction of flow is lessened so as to obtain maximum heat transfer and maintain a low pressure drop.

The constructions described are of particular utility in gas turbine cycles wherein heat is to be abstracted from the gases at low pressure and having a low density and low mass velocity. Because of such conditions it is important that the flow be well broken up on the gas side and the pin-like fins formed by the wire strips constitute a most efficient heating surface because the gas film is constantly broken up by them.

Heat exchangers embodying pin-fin extended surface in accordance with the invention may readily be adapted for transferring heat between various fluids because the ratio of the heat transfer surface contacted by a fluid flowing on one side of an intervening passage wall to the amount of surface on the other side of the wall and in contact with the other fluid may readily vary to suit conditions imposed by the particular fluids.

Although specific embodiments of the inven-.'

tion have been described in detail herein many changes and variations may be mad without departing from the essentials of the invention and, therefore, it is desired and intended that all such changes and variations be included within the scope of the following claims.

This is a division of the application filed in our name under Serial No. 752,008, on June 3, 1947; now Patent No. 2,595,457, granted May 6,

What is claimed is:

1. In a heat exchanger having a metallic plate constituting a fluid passage wall through which heat is conducted and formed with parallel undulations extending at an angle to the direction of fluid flow along said wall; heat exchange fins projecting from said wall each consisting of an individual metallic wire of uniform cross-section bent in sinusoidal form to provide a plurality of alternately upright and inverted substantially U- shaped loops therein with leg portions extending in upright relation from said wall and with intervening stretcher or yoke portions of alternate loops bent to extend parallel to each other so that the yoke portions of said alternate U-loops fit into the dwells of the undulations in the wall of said passage; and good heat transfer bonds between said stretcher portions of said loops and direction of fluid flow through said passage; and heat exchange fins bonded to said walls each consisting of an individual metallic wire of uniform cross-section bent in sinusoidal form to provide a plurality of alternately upright and inverted substantially U-shaped loops therein with leg portions extending as fins from said walls with intervening stretcher or yoke portions that connect leg portions of said U-loops that are contiguous along the axis of each wire contacting said plates over their length and being bent to extend at angles with respect to stretcher portions contiguous thereto along said wire that correspond to the relative angularity of the undulations in said plates so that the yoke portions of the contiguous U-loops fit into the dwells of the undulations in the opposite plate-walls that bound said passage.

3. In a heat exchanger having a metallic plate constituting a fluid passage wall through which heat is conducted and formed with parallel undulations extending at an angle to the direction of fluid flow along said wall; heat exchange fins bonded to said walls each consisting of an individual metallic wire of uniform cross-section bent in the alternate loops to extend parallel with each other and at angles with respect to the direction of fluid flow in said passage that cor respond to the angularity of the undulations in said plates with respect to the direction of fluid flow so that the stretcher portions of said alternate U-loops fit into the dwells of the undulations in said plate-wall that bounds said passage.

SVEN HOLM. ARTHUR JENSEN.

References Cited in the file of this patent,

UNITED STATES PATENTS Number Name Date 2,596,642 Boestad May 13, 1952 FOREIGN PATENTS Number Country Date 865,252 France May 16, 1941 

